The present invention relates to an ink jet recording head, and in particular, to an ink jet recording head for ejecting toner particles of liquid ink onto a recording media by electrostatic force and thereby achieving a recording operation.
FIG. 1 shows a conventional example of an ink jet recording head, which has been described in the Japanese Patent Laid-Open Publication No. 5-254118.
The ink jet head of FIG. 1 includes a plurality of nozzles 55a for ejecting ink therefrom, an ink stream path 54a connected to the nozzles 55a, a pressure generating element 56 for generating an ink ejecting pressure in the ink path 54a, and voltage applying means 58 for applying a voltage to the pressure generating element 56. Employed as the recording ink is pigment dispersion ink. In addition, there are disposed in the ink path 54a a plurality of segment electrodes 53 for mixing the pigment in the ink to obtain a uniform density thereof. Each segment electrode 53 is linked with a driver circuit 51 including potential difference generating means.
When a driving voltage pulse is applied to the segment electrodes 53 to alternately generate a potential difference therebetween, micro-particles of solid pigment having a negative charge are electrically moved by electrophoresis to prevent precipitation and coagulation of pigment particles.
FIG. 2 shows another conventional example of the ink jet recording apparatus described in the Japanese Patent Laid-Open Publication No. 61-57343.
The recording apparatus shown in FIG. 2 includes an ink chamber 68 to be filled with insulating ink, a porous member 69 arranged in the ink chamber 68, pump means (not shown) to flow ink into the porous member 69, a nozzle 70 coupled with the ink chamber 68, a signal electrode 61 disposed in the nozzle 70, and a rear electrode 62 provided to oppose to the signal electrode 64 with a recording media 64 arranged therebetween. In this structure, when a signal voltage is applied to the signal electrode 61, there is produced an electric field between the signal electrode 61 and the rear electrode 62 such that ink particles are ejected from a tip end of the nozzle 70 onto the recording media 64, thereby achieving a recording operation. In the system, the liquid ink flows through the porous member 69 by a pressure generated by the pump means, not shown, and is thereby electrically charged.
However, the conventional example described in the Japanese Patent Laid-Open Publication No. 5-254118 requires a plurality of pressure generating elements made of a piezoelectric substance to jet or eject the pigment ink and hence is attended with a disadvantage that the size of the ink jet recording head is increased. Additionally, there is employed a method in which the ink is ejected according to displacement of the piezo-electric material, namely, the pigment is not emitted by use of the electric field. Consequently, the precision of the ink ejecting direction considerably depends on the contour of nozzles and the like. Moreover, since it is necessary to fabricate a fine nozzle hole for each recording dot, the improvement of recording resolution is limited.
In addition, in the prior art example described in the Japanese Patent Laid-Open Publication No. 61-57343, due to the porous member disposed in the ink chamber to electrically charge the ink particles, there exist disadvantages that the recording head is increased in size, the head manufacturing job becomes difficult, and a high-power pump is necessary to supply ink to the nozzle through the porous member developing a high resistance against the ink stream.